.sidebar-nav {
  margin-top: 20px;
  padding: 0;
  list-style: none;
}
<!-- Add additional CSS in static file -->
{% load static %}
<link rel="stylesheet" href="{% static 'css/styles.css' %}" />

{% load static %}
<img
  src="{% static 'images/local_library_model_uml.png' %}"
  alt="UML diagram"
  style="width:555px;height:540px;" />
